A combine harvester, or a combine, is a machine that is used to harvest grain crops. The objective is to complete several processes, which traditionally were distinct, in one pass of the machine over a particular part of the field. Among the crops that may be harvested with a combine are wheat, oats, rye, barley, corn, soybeans, flax or linseed, and others. The waste (e.g., straw) discharged on the field includes the remaining dried stems and leaves of the crop which may be, for example, chopped and spread on the field as residue or windrowed and subsequently baled for feed and bedding for livestock.
A combine harvester cuts crop using a wide cutting header. The cut crop may be picked up and fed into the threshing and separating mechanism of the combine, typically consisting of a rotating threshing rotor or cylinder to which grooved steel bars, commonly referred to as rasp bars or threshing elements, may be bolted. These rasp bars thresh and aid in separating the grains from the chaff and straw through the action of the drum against the concaves, i.e., shaped “half drum,” that may also be fitted with steel bars and a meshed grill, through which grain, chaff and smaller debris may fall, whereas the straw, being too big or long, is carried through to the outlet. The chaff, straw, and other undesired material are returned to the field via a spreader mechanism.
In an axial flow combine, this threshing and separating system serves a primary separation function. The harvested crop is threshed and separated as it is conveyed between a longitudinally arranged rotor and the inner surface of an associated chamber comprising threshing and separating concaves, and a rotor cage or cover. The cut crop material spirals and is conveyed along a helical path along the inner surface of the chamber until substantially only larger residue remains. When the residue reaches the end of the threshing drum, it is expelled out of the rear of the combine. Meanwhile, the grain, chaff, and other small debris fall through the concaves and grates onto a cleaning device or shoe. For ease of reference, this smaller particulate crop material that contains the grain and chaff is referred to as threshed crop. The grain still needs to be further separated from the chaff by way of a winnowing process.
Clean grain is separated out of the threshed crop by way of a flat oscillating cleaning system that can include a chaffer and sieves. Generally, the cleaning system operates by mechanical and pneumatic methods; blowing air through the threshed crop to winnow the chaff and then sieving the grain to separate the grain from other particulates. Clean grain that is separated from residue via the sieves is typically transported to a grain tank in the combine for temporary storage. The grain tank is typically located atop the combine and loaded via a conveyer that carries clean grain collected in the cleaning system to the grain tank.
In normal operation, the waste product is generally expelled out the back of the combine. The waste product such as straw is either evenly spread via a set of spreader disks or windrowed for picking up via another machine such as a baler. Typically, the combine will windrow the chaff, which is generally in a first stream, discharged by a threshing rotor via a discharge beater or integral chopper and is positioned above a cleaning system. The smaller particles that pass through threshing concave grates includes the grain and the chaff, which is discharged onto the cleaning system for winnowing. The chaff is blown rearward by a cleaning fan in a second stream, which is generally below the straw path (the first stream).
FIG. 1 illustrates a typical spreader arrangement. The spreader disks 102 and 104 are attached and secured to a frame 106. The frame typically includes two or more cross-members 108 for providing support for the disks 102 and 104 when spinning. A motor 110, including a series of belts, gears or other drive systems is provided for the operation of the disks 102 and 104. A more detailed explanation of a spreader assembly is provided in U.S. Pat. No. 7,487,024, the content of which is hereby incorporated by reference in its entirety.
Generally, the chaff material flows in the direction of arrow A over the spreader disks 102 and 104, which catch a portion of the chaff and throw a portion of the chaff about the rear of the combine. When the combine is configured for windrowing, a windrow hood or other similarly apparatus diverts the flow of straw over the disks 102 and 104 and frame 106 to an opening in the back of the combine. However, as combine output has increased, this arrangement has resulted in straw and chaff back-up due to the inability of the straw to clear any frame structures and belts associated with the drive system. As such, when windrowing a large quantity of straw, a build-up can occur in the spreader disk assembly compartment, in effect building a straw bale in the compartment.
Another way to achieve windrowing requires pivoting the spreader out of the straw flow path, such as rearward and upward to allow the entire residue to discharge directly behind the combine and not be spread. Alternatively, the spreader disks could be removed from the drive shaft to windrow the entire crop residue (such as the spreader assembly as shown in FIG. 1). However, both of these configurations have the limitation that the combine cannot windrow the straw and spread the chaff simultaneously. In some instances, it may be preferable to have baled straw that is free from chaff and the chaff is discharged back onto the field by the spreader assembly to be reincorporated into the soil.